STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

FRANK  W.  DE  WOLF,  Chief 


Cooperative  Mining  Series 

BULLETIN  21 


THE  MANUFACTURE  OF  RETORT  GOAL- 
GAS  IN  THE  CENTRAL  STATES  USING 
LOW-SULPHUR  COAL  FROM  ILLINOIS, 
INDIANA  AND  WESTERN  KENTUCKY 


By 

W.  A.  J)DNKLEY,   State  Geological  Survey 

and 

W.  W.  ODELL;  U.  S.  Bureau  of  Mines 


ILLINOIS  MINING  INVESTIGATIONS 

Prepared   under  a   cooperative  agreement  between   the  Illinois  State  Geological   Survey 

Division,  the  Engineering   Experiment  Station  of  the  University  of  Illinois, 

and  the  U.  S.  Bureau  of  Mines, 


^csbskSs: 


PKINTED    BY   ATTTHOKITY   OF  THK    STATK   OK   ILLINOIS 


URBAnA,  ILLINOIS 
1918 


ILLINOIS  MINING  INVESTIGATIONS 

Cooperative  Agreement 

GAS  SECTION 

The  difficulty,  due.  to  war  conditions,  of  obtaining  adequate 
and  reliable  delivery  of  eastern  gas-coal  and  of  coke  has  sug- 
gested the  wider  use  in  gas  manufacture  of  low^-sulphur  coal 
mined  in  the* central  district,  comprising  Illinois,  Indiana,  and 
western  Kentucky. 

The  needs  of  the  gas  industry,  and  the  desire  of  the  U.  S. 
Fuel  Administration  to  meet  those  needs,  has  led  to  the  appoint- 
ment by  Governor  Frank  0.  Lowden,  of  a  Technical  Committee 
on  Gas,  By-products,  and  Public  Utilities,  to  act  in  an  advisory 
relation.  The  committee  includes  representatives  of  the  Illinois 
Gas  Association,  the  U.  S.  Bureau  of  Mines,  the  Engineering 
Experiment  Station  of  the  University  of  Illinois,  and  the  State 
Geological  Survey  Division  of  the  Department  of  Registration 
and  Education,  State  of  Illinois. 

Previously,  some  studies  of  the  use  of  Illinois  coal  in  retort- 
gas  manufacture  and  in  by-product  coke  ovens,  and  of  the  chem- 
ical and  physical  properties  of  Illinois  coal,  have  been  conducted 
under  the  Illinois  Mining  Investigations,  cooperative  agreement, 
— a  joint  agency  of  the  U.  S.  Bureau  of  Mines,  the  University  of 
Illinois,  and  the  State  Geological  Survey  Division.  The  continua- 
tion and  expansion  of  this  work  has  been  recommended  by  the 
Technical  Committee  and  the  Fuel  Administration.  In  response 
a  Gas  Section  has  been  created,  and  experienced  gas  engineers, 
chemists,  and  other  specialists  have  undertaken  a  program  of 
experiment  on  a  commercial  scale  to  extend  the  use  of  central  dis- 
trict coal  in  water-gas  generators  and  in  gas  retorts. 

The  results  of  the  investigations  will  be  published,  and,  in 
addition,  the  operators  of  gas  plants  in  the  region  naturally  trib- 
utary to  central-district  coal  will  be  advised  by  the  Technical 
Committee,  of  the  progress  from  time  to  time,  and  will  be  urged 
to  witness  and  participate  in  the  tests  and  to  introduce  in  their 
own  plants  new  or  improved  practices  which  will  lessen  the  bur- 
den on  the  railroads,  and  assist  the  mines  and  the  coke  ovens  to 
meet  the  unprecedented  demands  due  to  the  war. 

Inquiries  and  suggestions  regarding  the  gas  experiments 
should  be  addressed  to  Gas  Section,  Room  305  Ceramics  Bldg., 
Urbana,  Illinois. 


3  3051  00006  4067 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

FRANK  W.  DE  WOLF,  Chief 
Cooperative" Mining  Series 

BULLETIN  21 


THE  MANUFACTURE  OF  RETORT  GOAL- 
GAS  IN  THE  GENTRAL  STATES  USING 
LOW-SULPHUR  GOAL  FROM  ILLINOIS, 
INDIANA  AND  WESTERN  KENTUGKY 


By 

W.  A.  DUNKLEY,   State  Geological  Survey 

and 

W.  W.  ODELL;  U.  S.  Bureau  of  Mines 


ILLINOIS  MINING  INVESTIGATIONS 

Frepared  under  a  cooperative  agreement  between  the  Illinois  State  Geological   Survey 

Division,  the   Engineering   Experiment  Station  of  the  University   of  Illinois. 

and  the  U.  S.  Bureau  of  Mines. 


PRINTED   BY   AUTHORITY  OF  THE    STATE   OK   ILLINOIS 


IJKBANA.  ILLINOIS 
1918 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

Frank  W.  DeWolf,  Chief 


Committee  of  the    Board    of   Natural    Resources    and 
Conservation 

Francis  W.  Shepardson,  Chairman 

Director  of  Registration  and  Education 

David  Kinley 

Representing  the  President  of  the  Uni- 
versity of  Illinois 

Thomas  C.  Chamberlin 
Geologist 


CONTENTS 


PAGE 

War  adjustment  of  gas-coal  distribution  9 

Present  use  of  central  district  coal  9 

Problems   in   the  use   of  central   district  coals   in   coal-gas   manu- 
facture      11 

Price  and  availability  of  coals 11 

Plant   capacity    11 

Operating  labor   14 

Disposal  of  coke  14 

Purification    14 

Operating   methods 15 

Results  reported  from  central  district  coals  17 

Economical  advantage  of  central  district  coals  for  coal-gas  manu- 
facture      19 

Cost  of  materials  20 

Operating  labor  costs  21 

Repair   costs   21 

Overhead  and  miscellaneous  expense  22 

Income  from  residuals  22 

Summary  of  costs  23 

Summary   24 


(5) 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://archive.org/details/manufactureofret21dunk 


ILLUSTRATIONS 


FIGURE  PAGE 

1.  Bituminous  coal  zone  C 8 

2.  Bituminous  coal  zone  D  10 

3.  Bituminous  coal  zone  E  13 


TABLES 


1.  Results  of  retort-gas  practice  with  central  district  coals  from 

Illinois     18 

2.  A  comparison  of  the  approximate  manufacturing  costs  of  gas 

from  central  district  and  eastern  gas-coals 23 


(7) 


Fig.  1. — Bituminous  coal  zone  C,  established  by  the  U.  S.  Fuel  and  the 
U.  S.  Railroad  Administrations,  April  1,  1918,  and  corrected  to  July  1.  1918. 
Includes  low-sulphur  coal  areas  in  southern  Illinois. 

During  the  period  from  October  1,  1918  to  March  31,  1919,  producing  districts  of  Illi- 
nois, shown  in  black,  are  restricted  in  their  shipments  of  coal  to  markets  within  and  along 
the  solid  boundary  line. 

During  the  period  from  April  1,  1918,  to  September  30,  1918,  these  same  districts  are 
restricted  in  their  shipments  to  markets  within  and  along  the  heavy  dashed  boundary  line 
and  its  solid  continuation  south  from  Albia,  Iowa,  and  Milwaukee,  Wisconsin. 

During  the  entire  year  the  producing  districts  of  Vermilion  County,  Illinois,  along  the 
Wabash  Railway  may  in  addition  ship  coal  to  points  of  delivery  along  the  Wabash   Railway 


THE  MANUFACTURE  OF  RETORT  GOAL-GAS 

IN  THE  CENTRAL  STATES 

USING  LOW-SULPHUR  COAL  FROM  ILLINOIS, 

INDIANA  AND  WESTERN  KENTUCKY 

By  W.  A.   Dimkley,   State  Geological  Survey, 
and  W.  W.  Odell,  U.  S.  Bureau  of  Mines 


WAR  ADJUSTMENT  OF  GAS-COAL  DISTRIBUTION 
Eastern  gas  coals,  because  of  their  high  yield  of  gas  and  of 
excellent  coke,  have  hitherto  been  used  almost  exclusively  for  re- 
tort coal-gas  manufacture  in  the  central  west  as  well  as  in  the 
east.  However,  the  necessity  of  avoiding  long  freight  hauls 
wherever  possible,  and  of  conserving  the  supply  of  eastern  coals 
for  the  manufacture  of  metallurgical  coke  and  for  eastern  gas 
requirements  makes  it  a  patriotic  duty  to  utilize  as  far  as  possible 
the  great  but  comparatively  undeveloped  resources  of  low-sulphur 
coal  in  the  central  states. 

Gas  plants  in  zones  C,  D,  and  E  of  the  U.  S.  Fuel  Admini- 
stration (figs.  1,  2,  and  3  and  explanations  of  subsequent 
changes)  should  naturally  use  coal  mined  within  the  zones  if 
possible,  rather  than  request  coal  under  permit  from  distant 
sources.  The  term  "central  district"  coal  as  used  in  this  paper 
includes  that  from  Illinois,  Indiana,  and  western  Kentucky. 

Although  both  commercial  and  technical  problems  must  be 
solved  before  these  coals  are  generally  used  in  gas  manufacture, 
reliable  data  already  collected  warrant  further  effort  and  prom- 
ise success. 

PRESENT  USE  OF  CENTRAL  DISTRICT  COAL 
The  use  of  central  district  coals  in  gas  making  is  by  no  means 
new.  These  coals  have  been  used  in  a  majority  of  the  20  repre- 
sentative plants  recently  inspected  in  Illinois,  Iowa,  and  Wiscon- 
sin. Depending  upon  local  conditions,  the  results  obtained  vary 
considerably  and  are  in  general  agreement  with  those  reported 


within  Indiana.  Similarly,  producing  districts  of  Sangamon  County  may  ship  to  stations 
along  the  Cincinnati,  Indianapolis,  and  Western  Railroad,  as  far  east  as  Indianapolis,  and 
including  points  of  delivery  within  switching  limits  on  connecting   lines. 

A  modification  affecting  the  distribution  of  Jackson  and  Randolph  county  coals  is  as 
follows:  All  producers  located  along  the  Mobile  and  Ohio  Railroad  and  short-line  connections 
in  Illinois  may  ship  coal  to  points  of  delivery  on  the  Mobile  and  Ohio  Railroad  within  Ten- 
nessee and  Mississippi,  as  far  south  as  Meridian,  Mississippi,  including  stations  within 
switching  limits  on  connecting   railway  lines. 

Consult  the  District  Representative  of  the  U.  S.  Fuel  Administration,  2017  Fisher 
Building,  Chicago,  to  learn  decisions  on  suggested  changes  still  ponding.  Of  these  changes, 
the  one  affecting  particularly  the  coal-gas  industry  relates  to  the  addition  of  the  Lower 
Peninsula  of  Michigan  to   Zone  C 


10 


RETORT    COAL-GAS    MANUFACTURE 


by  F.  K.  Ovitz1  of  the  U.  S.  Bureau  of  Mines.  Mr.  Ovitz's  work 
had  to  do  almost  exclusively  with  the  manufacture  of  coal  gas 
from  Illinois  coals  and  mixtures  of  these  with  other  coals.  Since 
the  publication  of  his  results,  much  creditable  work  has  been  done 
by  individual  companies  on  the  use  of  Illinois  coals  in  water-gas 
generators.  A  separate  paper  by  the  authors  of  this  report  has 
been  prepared,  dealing  with  that  work. 


Fig.  2. — Bituminous  coal  zone  D,  established  by  the  U.  S.  Fuel  and  the 
U.  S.  Railroad  Administrations,  April  1,  1918.  Includes  low-sulphur  coal 
areas  in  southwestern  Indiana. 

All  producing  districts  of  Indiana,  shown  in  black,  are  restricted  in  their  shipments  of 
coal  to  markets  within  or  along  the  heavy  boundary  line. 

Consult  the  District  Representative  of  the  U.  S.  Fuel  Administration,  2017  Fisher 
Building,  Chicago,  to  learn  decisions  on  a  number  of  suggested  changes  still  pending  at  the 
time  this  was  printed. 

This  report  is  the  result  of  an  inspection  made  by  W.  A. 
Dunkley,  gas  engineer  of  the  Illinois  Geological  Survey,  and 
W.  W.  Odell,  gas  engineer  of  the  U.  S.  Bureau  of  Mines,  working 


^vitz,  F.  K.,  Coking  of  Illinois  coals,  U.  S.  Bureau  of  Mines  Bull.  138,  1917. 

— .,    Carbonization    of   Illinois    coals    in    inclined    gas    retorts:    111.    State    Geol. 
Survey,   Cooperative  Series  Bull.   20,   1918. 


PROBLEMS  11 

under  the  cooperative  agreement2,  in  order  to  determine  and  re- 
port at  once  the  experiences  of  various  coal-gas  manufacturers 
with  central  district  coals.  The  differences  in  present  practice 
form  the  basis  of  a  program  of  further  experimentation. 

PROBLEMS  IN  THE  USE  OF  CENTRAL  DISTRICT  COALS 
IN  COAL-GAS  MANUFACTURE 
The  operator  who  has  been  accustomed  to  use  eastern  gas 
coals  and  whose  plant  and  operating  conditions  are  laid  out  es- 
pecially for  these  coals  is  confronted  by  new  problems  when  the 
use  of  central  district  coals  is  contemplated.  These  problems  in- 
clude relative  prices  and  availability  of  coal  supplies,  plant  capac- 
ity, labor  supply,  disposal  of  coke,  purification  of  the  gas,  and 
changes  in  operating  methods.  These  problems  will  be  discussed 
separately. 

1.  Price  and  Availability  of  Coals 
The  prices  of  both  eastern  and  central  district  gas  coals  are 
continually  changing.  Owing,  however,  to  the  considerably  longer 
haul  in  the  former  case,  there  is  usually  about  $2.00  per  ton  mar- 
gin between  the  delivered  price  of  eastern  and  of  central  district 
coals,  in  favor  of  the  latter.  For  example,  some  plants  in  Illinois 
report  that  eastern  coals  are  now  costing  them  about  $6.00  per 
ton  and  central  district  coals  from  the  southern  Illinois  fields, 
about  $4.00  per  ton.  A  difference  in  price  at  least  equal  to  this 
seems  likely  to  be  maintained  for  plants  in  Illinois  and  the  states 
to  the  west. 

The  length  of  haul  from  the  southern  Illinois  mines  to  gas 
plants  in  the  northern  part  of  the  State  varies  from  250  to  350 
miles.  On  the  other  hand,  the  rail  haul  from  the  eastern  gas-coal 
fields  to  the  same  region  averages  probably  at  least  twice  as  long 
and  in  at  least  one  case  is  720  miles.  Taking  into  consideration 
the  immense  freight  traffic  for  other  purposes  on  the  east  and 
west  lines,  especially  through  the  Pittsburgh  district,  it  seems 
reasonable  to  expect  that  the  supply  of  central  district  coals  to 
local  plants  would  be  more  certain  during  freight  congestion  than 
would  the  supply  of  eastern  coals.  Since  the  yearly  gas-coal  re- 
quirement of  Zone  C  alone  is  nearly  2,000,000  tons,  an  extensive 
substitution  of  central  district  coals  for  eastern  coals  would  re- 
lease many  cars  on  the  east  and  west  roads  for  other  purposes. 


2An  extensive  investigation  of  coal  and  coal  mining  has  been  in  progress  since  1911 
under  a  cooperative  agreement  between  the  U.  S.  Bureau  of  Mines,  the  Illinois  State  Geolog- 
ical Survey  and  the  Engineering  Experiment  Station  of  the  University  of  Illinois. 


12  RETORT    COAL-GAS   MANUFACTURE 

2.     Plant  Capacity 

The  experiences  of  those  who  have  used  central  district  coals 
show  that  under  usual  operating  conditions,  these  coals  do  not 
yield  more  than  80  per  cent  of  the  amount  of  gas  yielded  by  an 
equal  weight  of  good  eastern  gas  coal.  The  question  of  plant 
capacity  is  therefore  one  of  first  importance.  If,  as  is  the  case  at 
some  plants,  hardly  enough  generating  apparatus  is  provided  to 
meet  the  demand  for  gas  when  the  highest  yields  are  obtained 
from  eastern  coals,  then  an  immediate  change  to  central  district 
coals  is  impracticable.  On  the  other  hand,  if  a  plant  has  at  least 
20  per  cent  spare  capacity,  this  obstacle  of  decreased  capacity  is 
overcome.  At  many  plants  where  there  is  a  rated  surplus  ca- 
pacity, the  spare  benches  are  down  for  repairs  and  may  not  be 
repaired  until  actually  needed  for  use.  In  many  cases  if  this  sur- 
plus capacity  could  be  quickly  made  available  there  would  be  no 
obstacle  to  the  use  of  central  district  coals  until  other  benches 
were  let  down  for  repairs. 

In  some  plants  it  was  observed  that  all  the  coal-gas  appar- 
atus is  worked  constantly  to  maximum  capacity,  and  the  addi- 
tional gas  required  is  supplied  by  water-gas  apparatus.  In  such 
cases  the  substitution  of  central  district  for  eastern  coals  in  the 
coal-gas  plant  would  necessitate  the  making  of  more  water  gas. 
The  question  would  have  to  be  decided  whether  the  saving  in  cost 
of  gas  manufacture  by  the  use  of  central  district  coals  would  be 
offset  by  the  additional  cost  of  making  the  extra  volume  of  water 
gas  needed,  since  the  cost  of  water-gas  manufacture  is  usually 
higher  than  coal  gas.  In  such  cases,  if  ample  water-gas  apparatus 
is  available,  the  use  of  central  district  coals  as  generator  fuel 
might  permit  a  substantial  saving  in  this  part  of  the  plant. 
Under  favorable  conditions,  therefore,  the  use  of  central  district 
coals  throughout  the  plant  might  be  found  quite  profitable.  This 
leaves  out  of  account  the  desirability,  especially  at  the  present 
time,  of  conserving  the  transportation  facilities  of  the  country, 
which  should  be  seriously  considered  by  every  gas  man. 

Several  plants  were  visited  in  which  the  use  of  eastern  gas 
coals  is  not  absolutely  necessary  but  is  continued  either  because 
no  financial  advantage  is  seen  from  making  a  change,  or  because 
the  troubles  anticipated  from  the  use  of  central  district  coals  are 
magnified.  Where  the  total  capacity  of  the  plant  would  permit 
the  use  of  central  district  coals,  alone  or  in  mixtures,  this  matter 
should  have  the  earnest  consideration  of  the  manager,  especially 
since  their  use  may  become  necessary  in  a  few  months  on  account 
of  freight  congestion. 


PROBLEMS 


13 


Fig.  3. — Bituminous  coal  zone  E,  established  by  the  U.  S.  Fuel  and  the 
U.  S.  Railroad  Administration,  April  1,  1918,  and  corrected  to  July  1,  1918. 
Includes  low-sulphur  coal  in  western  Kentucky. 

Producing-  districts  in  western  Kentucky,  shown  in  black,  arc  restricted  in  their  ship- 
ments of  coal  to  markets  within  or  along  the  heavy  boundary  line. 

Modifications  of  the  original  zoning  made  prior  to  July  1,  1918,  have  been  incorporated 
in  the  map.    Later  modifications  affecting  the  gas-coal  markets  are  as  follows: 

Producers  in  the  western  Kentucky  districts  may  in  addition  distribute  their  coal  (1) 
along  the  Louisville,  Cincinnati  and  Lexington  Division  of  the  Louisville  and  Nashville  Rail- 
way between  Louisville  and  Newport,  Kentucky,  inclusive,  and  (2)  in  Cincinnati,  Ohio,  and 
points  of  delivery  located  within   the  Cincinnati  switching  district. 

Producers  in  this  district  may  not  ship  coal  without  permit  into  those  parts  of  Illinois, 
Wisconsin,  and  Indiana,  included  originally  in  zone  E  as  shown  by  the  heavy  boundary  line. 
A  provision  is  made,  however,  which  should  be  noted  by  the  coal-gas  manufacturer:  Any 
western  Kentucky  producer  may  ship  coal  of  special  quality  for  special  uses  to  delivery  points 
within  the  prohibited  territory  under  permit  which  may  be  obtained  from  the  Fuel  Admin- 
istration on  application  of  the  consumer. 


14  RETORT    COAL-GAS    MANUFACTURE 


3.     Operating  Labor 


An  occasional  plant  was  inspected  in  which  there  is  appar- 
ently ample  generating  capacity  in  good  condition  to  handle  cen- 
tral district  coals,  but  the  management  is  not  using  them  because 
of  the  difficulty  of  securing  the  additional  retort  house  labor  to 
operate  the  necessary  additional  equipment.  In  these  cases  it  is 
impossible  to  judge  from  casual  inspection  whether  the  labor 
situation  is  really  as  serious  as  reported,  or  whether  the  policy 
of  the  particular  company  in  dealing  with  its  employees  is  re- 
sponsible for  the  difficulty.  In  one  plant  visited  the  labor  short- 
age is  so  serious  that  in  an  effort  to  maintain  the  gas  supply 
without  starting  another  bench,  heavy  charges  are  made  and 
pulled  so  "green"  that  the  gas  obtained  is  not  more  than  80  per 
cent  of  the  yield  which  could  be  reasonably  expected  from  the 
eastern  coal  in  use.  It  is  evident  that  the  money  being  lost  would 
far  more  than  offset  the  readjustment  of  wage  which  might  be 
necessary  to  put  the  plant  on  an  efficient  operating  basis. 

4.    Disposal  of  Coke 

Nearly  all  the  gas  operators  interviewed  stated  that  the  cen- 
tral district  coals  produce  coke  which  is  inferior  to  that  obtained 
from  the  best  eastern  coals;  yet  it  is  quite  generally  agreed  that 
they  can  sell  at  the  present  time  all  the  coke  which  they  can  pro- 
duce from  either  kind  of  coal.  Some  plants  could  dispose  of  sev- 
eral times  their  present  production  from  central  district  coal  at 
a  profit. 

With  the  return  to  normal  conditions  of  demand  and  supply, 
the  quality  and  yield  of  coke  from  central  district  coals  will  be 
of  renewed  importance;  and  therefore  a  study  of  the  conditions 
affecting  these  will  be  made  as  soon  as  possible. 

In  the  use  of  these  cokes  as  water-gas  generator  fuel  the 
experiences  of  various  operators  differ.  Some  operators  have 
much  trouble  with  the  clinker  formed  from  these  cokes,  while 
others  handle  the  clinkers  without  particular  difficulty.  Further 
study  of  clinker  formation  is  needed  and  will  be  made  in  the  near 
future.  Operators  who  are  using  central  district  coals  as  gener- 
ator fuel  in  water-gas  machines  usually  report  less  clinker  diffi- 
culty than  where  the  coke  made  from  the  same  coals  is  used.  This 
indicates  that  the  operating  conditions  in  the  generator  are  of  at 
least  as  great  importance  as  the  composition  of  the  fuel  and  ash. 


PROBLEMS  15 

5.  Purification 
Many  operators  beginning  the  use  of  central  district  coals 
anticipate  that  a  much  larger  amount  of  sulphur  will  be  yielded 
in  the  gas  from  these  coals  than  from  eastern  coals.  One  oper- 
ator who  has  never  used  central  district  coals  states  that  there  is 
not  enough  purifying  material  in  the  United  States  to  purify  the 
gas  from  one  carload  of  Illinois  coal !  While  it  is  true  that  many 
coals  of  this  district  can  not  be  used  under  present  conditions 
because  of  their  high-sulphur  content,  yet  there  are  many  coals 
produced  in  the  central  district  which  are  nearly  as  low  in  sul- 
phur content  as  eastern  coals.  A  subsequent  publication  will  pre- 
sent a  description  of  the  low-sulphur  coals  mined  in  the  central 
district.  Few  companies  who  have  used  these  coals  report  any 
serious  difficulty  from  excess  sulphur  in  the  gas.  Where  sulphur 
has  caused  trouble,  it  is  usually  impossible  to  learn  definitely 
whether  the  sulphur  in  the  gas  has  been  excessive  or  whether  the 
purifying  material  in  use  at  that  time  was  inefficient.  In  most 
of  the  plants  inspected  there  are  no  facilities  for  making  quanti- 
tative tests  of  sulphur  in  the  gas.  The  more  general  use  of  the 
Tutweiler  hydrogen  sulphide  apparatus  among  the  various  gas 
companies  would  seem  to  be  advantageous.  In  most  of  the  plants 
visited,  the  purifying  capacity  is  ample  to  purify  the  gas  pro- 
duced from  any  of  the  better  coals  of  this  district. 

6.  Operating  Methods  with  Central  District  Coals 
So  far  as  can  be  learned  from  various  operators,  the  use  of 
central  district  coals  in  retort  gas  practice  at  present  is  in  gen- 
eral no  different  than  the  use  of  eastern  coals.  Practice  varies 
considerably  in  different  plants,  but  these  variations  are  due  to 
personal  views  of  different  operators  as  to  what  heats,  coking 
times,  weights  of  charge,  etc.,  give  the  best  results  in  their  par- 
ticular cases,  rather  than  to  any  generally  recognized  "best  way" 
of  using  these  coals.  With  the  considerable  differences  in  practice 
which  exist,  there  are  no  very  marked  variations  in  the  results 
obtained. 

In  carbonizing  coals  in  retort  practice  several  variable  con- 
ditions influence  the  quantity  and  quality  of  the  products.  Among 
these,  the  conditions  which  are  most  easily  changed  and  most 
likely  to  be  varied  by  different  operators  are:  retort  tempera- 
ture, length  of  coking  time,  size  of  charge,  and  size  of  coal.  One 
operator  favors  a  certain  combination  of  these  conditions  for  a 
given  coal,  while  another  operator  selects  a  different  combination. 
The  results  obtained  may  be  almost  identical. 


16  RETORT    COAL-GAS   MANUFACTURE 

Some  operators  favor  high  retort  temperature  for  central 
district  coals,  claiming  that  the  rate  of  heat  penetration  into  the 
charge  is  slower  than  with  eastern  coals,  and  that  high  tempera- 
ture is  necessary  to  obtain  complete  fusion  of  the  coal  and  conse- 
quent strong  coke  structure.  They  point  to  the  granular  structure 
of  the  coke  from  some  of  these  coals  as  evidence  of  incomplete 
coking  due  to  insufficient  temperature.  On  the  other  hand,  other 
operators  say  that  the  heat  penetration  is  more  rapid  with  these 
coals  and  that  a  poor,  weak,  fingery  coke  structure  is  more  liable 
to  result  from  over-coking  the  charge,  and  consequently  they 
favor  lower  retort  temperatures  for  these  coals. 

Long  coking  periods  are  preferred  to  short  periods  by  some 
operators.  They  often  claim  that  a  higher  yield  of  good  quality 
gas  and  a  higher  yield  of  ammonia  are  obtained  with  a  long 
period  of  coking  at  a  moderate  temperature  than  with  a  short 
coking  period  at  a  high  temperature.  On  the  other  hand,  some 
operators  say  that  a  long  coking  period  over-cokes  the  charge, 
weakens  the  structure  of  the  coke,  and  makes  it  more  liable  to 
break  into  small  fingery  pieces. 

Evidently  the  same  results  are  frequently  attributed  to  long 
coking  as  to  high  temperatures.  There  is  usually  no  way  of  deter- 
mining what  the  temperature  of  a  retort  actually  is.  Gas  plants 
are  not  generally  equipped  with  pyrometers,  and  the  degree  of 
temperature  carried  is  merely  a  matter  of  judgment,  into  which 
the  personal  opinion  enters  very  largely.  The  study  of  these  vari- 
ables would  give  much-needed  information,  and  it  is  hoped  that 
such  a  study  may  be  undertaken  soon. 

There  is  no  uniformity  in  the  weight  of  coal  charge  in  differ- 
ent plants  having  retorts  of  the  same  size.  Usually  the  charges 
are  as  large  as  can  be  properly  coked  in  the  chosen  coking  period 
and  vary  from  325  to  400  pounds.  The  weight  of  charge  seems 
to  be  the  means  of  heat  control  in  many  plants.  If  the  retort  tem- 
peratures drops,  the  weight  of  charge  is  decreased,  or  vice  versa. 
The  weight  of  charge  is  also  varied  to  diminish  standpipe  stop- 
page and  to  prevent  naphthalene  deposits.  So  far  as  could  be 
learned  no  difference  in  the  size  of  charge  is  required  with  cen- 
tral district  coals  and  with  eastern  gas  coals. 

Size  of  coal  is  another  varying  condition  about  which  great 
difference  of  opinion  is  expressed.  Fine  crushing  of  the  coal 
would  undoubtedly  result  in  a  more  intimate  mixture  of  all  the 
components  of  the  coal  and  result  in  a  more  uniform  and  stronger 
coke.  However,  there  is  considerable  difference  of  opinion  among 


RESULTS  17 

gas  men  as  to  the  feasibility  of  crushing  coal.  Only  a  very  few 
plants  are  equipped  with  crushers.  Some  operators  claim  that 
whereas  the  quality  of  coke  from  crushed  coal  would  be  better, 
the  heat  penetration  into  crushed  central  district  coal  is  so  slow 
that  the  usual  yield  of  gas  is  not  obtained  from  the  coal  during 
the  short  coking  period  which  the  retort  gas  maker  can  allow. 
However,  at  least  one  inclined-retort  plant  was  inspected  which 
is  coking  crushed  coal  and  obtaining,  not  only  a  very  good  coke 
from  southern  Illinois  coal,  but  a  yield  of  gas  greater  than  is 
produced  by  most  plants  using  uncrushed  coal.  From  appear- 
ances, the  coal  is  thoroughly  coked  in  6  hours.  Some  operators 
expressed  novel  opinions  and  theories  upon  the  coking  of  various 
coals,  and  though  these  ideas  have  no  place  in  this  report,  they 
suggested  problems  for  further  study. 

RESULTS  REPORTED  FROM  CENTRAL  DISTRICT  COALS 

Several  of  the  coal-gas  plants  in  Illinois  are  using  eastern 
gas  coals  this  summer.  Some  of  these  plants  used  central  district 
coals  during  the  past  winter  or  at  some  previous  time,  but  the 
results  of  their  experiences  with  these  coals  are  available  chiefly 
as  more  or  less  definite  impressions.  The  following  are  typical  re- 
sults reported  where  definite  figures  are  available ;  unfortunately 
none  for  Indiana  or  western  Kentucky  is  included. 

These  results  are  in  fair  agreement  with  those  reported  by 
Mr.  Ovitz  and  indicate  that  no  radical  developments  in  the  use  of 
these  coals  in  ordinary  retort  practice  have  arisen  recently.  The 
central  district  coals  now  in  use  are  from  only  a  few  mines,  and 
it  seems  likely  that  much  valuable  information  can  be  obtained 
by  the  testing  of  other  coals  and  mixtures  of  coals  from  this  dis- 
trict. A  more  intimate  knowledge  of  such  conditions  as  tempera- 
ture, coking  time,  size  of  coal,  rate  of  heat  penetration,  and  other 
variables  is  also  needed.  This  information  can  come  only  by  ex- 
periment. 

Some  gas  men  believe  that  the  most  successful  use  of  central 
district  coals  will  come  through  new  by-product  oven  or  low-tem- 
perature processes,  rather  than  by  any  modification  of  operating 
conditions  in  the  present  equipment.  Certain  investigators  are 
working  on  such  processes,  and  some  attractive  claims  are  made 
for  them,  but  as  yet  no  commercial  plants  built  to  use  these  pro- 
cesses are  in  regular  operation  with  central  district  coals. 


18 


RETORT    COAL-GAS   MANUFACTURE 


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ECONOMICAL   ADVANTAGES  1ft 

Meanwhile,  the  type  of  gas  retort  now  in  general  use  is  an 
active  unit  whose  characteristics  are  understood  by  the  operators. 
It  has  been  in  use  for  years,  and  doubtless  will  continue  to  be 
used  in  the  smaller  plants  for  years  to  come.  It  represents  the 
investment  of  large  sums  of  money.  For  these  reasons  the  effect 
of  the  many  varying  conditions  upon  its  operations  should  be 
thoroughly  understood  as  a  basis  for  further  work  which  may 
be  done  from  time  to  time. 

THE  ECONOMICAL  ADVANTAGE  OF  CENTRAL  DISTRICT 
COALS  FOR  COAL-GAS  MANUFACTURE 

Aside  from  the  difficulty  of  obtaining  eastern  gas  coals  un- 
der present  conditions,  and  the  conservation  of  freight  traffic  to 
be  gained  by  the  use  of  coals  of  the  central  district  for  gas  mak- 
ing, the  question  of  the  choice  of  coals  is  a  financial  one :  whether 
it  is  actually  cheaper  for  the  gas  manufacturer  to  use  central 
district  coals. 

To  determine  what  if  any  saving  can  be  realized  from  the 
use  of  these  coals  in  a  given  case,  local  conditions  must  be  con- 
sidered and  certain  assumptions  based  upon  the  results  which 
have  been  obtained  by  others,  must  be  made.  It  is  the  purpose  of 
this  section  to  apply  the  average  operating  results  reported  by 
several  plants  to  a  case  in  which  certain  fuel,  labor,  and  miscel- 
laneous costs  and  returns  from  the  sale  of  residuals  are  assumed, 
and  to  point  out  how  the  various  conditions  affect  the  cost  of 
manufacture.  The  costs  assumed  do  not  represent  the  conditions 
existing  in  any  particular  plant,  but  are  taken  merely  for  illu- 
stration. It  is  believed  that  any  operator  can  substitute  his  own 
figures  and  arrive  at  a  conclusion  as  to  whether  the  use  of  cen- 
tral district  coal  would  pay  in  his  own  case. 

In  changing  from  eastern  to  central  district  coal,  several 
factors  are  to  be  considered  in  determining  the  effect  of  the 
change  on  the  final  cost  of  manufacture.  These  factors  include, 
for  each  coal,  the  following  items : 

1.  Cost  of  the  amounts  of  materials  required  to  produce  a 
given  volume  (say  1,000  cu.  ft.)  of  gas  of  the  required  quality. 

2.  Cost  of  operating  labor. 

3.  Cost  of  repairs. 

4.  Overhead  and  miscellaneous  expense. 


20  RETORT    COAL-GAS    MANUFACTURE 

It  is  very  difficult  except  after  long  operating  experience  to 
assign  definite  values  to  all  of  these  items,  and  in  some  cases  the 
difference  would  be  so  slight  as  to  have  little  weight  in  the  com- 
parison. In  assuming  values  for  the  different  items  the  unit  costs 
selected  do  not  apply  to  the  operating  conditions  in  any  particular 
plant.  The  amounts  of  materials  used,  however,  are  fairly  repre- 
sentative of  the  present  practice  in  several  plants. 

Cost  of  Materials 

In  the  following  comparison  it  is  assumed  that  central  dis- 
trict coal  can  be  delivered  at  the  gas  plant  for  $4.00  per  ton,  and 
that  eastern  coal  at  the  same  place  costs  $6.00  per  ton.  From 
the  results  obtained  in  several  plants,  yields  of  4.2  cubic  feet  of 
gas  per  pound  from  central  district  coals,  and  5.25  cubic  feet  of 
gas  from  eastern  coals  seem  to  be  typical  figures.  The  gas  coal 
cost  on  this  basis  would  be  $0,476  per  1,000  cubic  feet  with  cen- 
tral district  and  $0,571  per  1,000  cubic  feet  with  eastern  coal. 

The  cost  of  bench  fuel  in  each  case  will  of  course  depend 
upon  the  kind  of  fuel  used.  Most  of  the  plants  of  this  district  are 
now  using  for  bench  fuel  a  portion  of  the  coke  which  they  pro- 
duce. A  few,  however,  are  using  coal.  It  will  be  assumed  in  this 
case  that  coke  is  used  and  that  85  per  cent  of  the  coke  from  cen- 
tral district  coal  is  worth  $9.00  per  ton  and  the  remainder  is 
breeze  worth  $2.00  per  ton,  whereas  92  per  cent  of  the  eastern 
coke  is  worth  $9.00  per  ton  and  the  remaining  8  per  cent  is  worth 
$2.00  per  ton.  On  this  basis,  assuming  that  300  pounds  of  bench 
fuel  are  required  per  ton  of  coal  carbonized,  the  cost  in  the  case 
of  the  central  district  coal  will  be  $0,142  per  1,000  cubic  feet  of 
gas,  and  in  the  case  of  eastern  coal  $0,120  per  1,000  cubic  feet. 

No  present  prices  of  purifying  material  are  available,  and 
since  this  item  is  usually  a  relatively  small  one  in  making  up  the 
total  manufacturing  cost,  it  will  be  assumed  that  the  total  purify  - 
ig  cost,  including  labor  and  material,  is  $0,009  per  1,000  cubic 
feet  for  gas  made  from  eastern  coal,  and  50  per  cent  greater  or 
$0.0135  for  gas  from  central  district  coal. 

Other  materials  such  as  steam,  water,  lubricating  oils,  gas 
and  electric  current  enter  into  the  cost  of  manufacture,  but  ex- 
cept in  special  cases  where  coal  or  coke  is  handled  mechanically, 
it  does  not  seem  likely  that  the  cost  would  be  materially  different 
for  one  kind  of  coal  than  for  the  other.  In  this  case  it  will  be 
assumed  that  these  materials  are  handled  by  hand  and  the  differ- 
ence will  be  considered  under  operating  labor. 


ECONOMICAL   ADVANTAGES  21 


Operating  Labor  Costs 

The  operating  labor  will  be  assumed  to  include  coal  and 
coke  handling,  both  in  the  yard  and  in  the  retort  house ;  and  mis- 
cellaneous works-labor,  purifying  labor  and  work-superinten- 
dence. Of  these  items,  the  only  ones  which  appear  to  need  con- 
sideration in  a  comparison  of  this  kind  are  fuel-handling  labor 
and  purifying  labor.   The  latter  has  already  been  taken  up. 

In  using  central  district  coals  more  coal  must  be  handled  to 
produce  1,000  cubic  feet  of  gas  than  when  eastern  coal  is  used. 
On  the  basis  of  the  yields  of  gas  assumed,  namely,  4.2  cubic  feet 
of  gas  per  pound  from  the  former  coal  and  5.25  cubic  feet  of  gas 
from  the  latter,  the  amount  of  central  district  coal  to  be  handled 
would  be  25  per  cent  greater.  The  cost  of  handling  coal,  both  in 
the  yard  and  in  the  retort  house,  will  vary  according  to  the  pre- 
vailing scale  of  labor.  For  this  comparison  a  cost  of  20  cents  per 
ton  for  handling  in  the  yard  is  assumed,  which  would  give  a  cost 
of  $0,019  per  1,000  cubic  feet  of  gas  from  eastern  coal  and  $0,024 
per  thousand  cubic  feet  of  gas  from  central  district  coals.  For 
retort-house  labor,  which  includes  the  care  of  the  benches,  charg- 
ing and  discharging  the  retorts,  caring  for  the  standpipes  and 
hydraulic  main,  quenching  and  stocking  coke,  etc.,  a  cost  of  $1.50 
per  ton  is  assumed  which  would  amount  to  a  retort-house  labor 
cost  of  $0,178  for  central  district  coal  and  $0,142  for  eastern 
coal. 

Repair  Costs 

So  far  as  can  be  ascertained,  the  wear  and  tear  on  benches 
and  gas-handling  equipment  is  no  greater  per  ton  of  coal  car- 
bonized with  one  kind  of  coal  than  with  the  other.  But  about  25 
per  cent  more  generating  equipment  is  required  to  produce  a 
given  amount  of  gas  from  central  district  coal  than  from  eastern 
coal.  It  is  assumed  that  the  cost  of  bench  repairs  is  $0,045  per 
1,000  cubic  feet  of  gas  with  eastern  coal  and  that  the  repair  cost 
is  proportional  to  the  amount  of  equipment  in  use.  On  this  basis 
the  cost  of  repairs  with  central  district  coals  will  be  $0,056  per 
1,000  cubic  feet.  It  is  assumed  that  all  other  repair  costs  remain 
unchanged,  although  it  is  evident  that  in  a  plant  equipped  with 
much  coal-handling  equipment  the  handling  of  25  per  cent  more 
coal  would  necessarily  increase  the  cost  of  repairs  per  1,000 
cubic  feet  of  gas  by  an  appreciable  amount. 


22  RETORT    COAL-GAS    MANUFACTURE 

Overhead  and  Miscellaneous  Expense 
No  figures  are  available  from  which  it  is  possible  to  compute 
what  change  in  overhead  expense  would  result  from  the  change 
of  coals  here  considered.  If  more  equipment  had  to  be  installed 
to  make  the  use  of  central  district  coals  possible  and  the  interest 
on  the  investment,  depreciation,  etc.,  were  computed  to  the  basis 
of  1,000  cubic  feet  of  gas  made,  it  is  evident  that  there  would  be 
an  increase  in  the  cost  per  1,000  cubic  feet  for  gas  from  central 
district  coal.  On  the  other  hand,  if  hitherto  idle  equipment  were 
brought  into  use  then  the  cost  per  1,000  cubic  feet  due  to  the  use 
of  these  coals  might  actually  decrease,  since  there  would  be  a  re- 
turn from  the  capital  invested  on  account  of  increased  coke  pro- 
duction. In  the  present  case  the  effect  of  this  item  upon  the  rela- 
tive cost  will  not  be  considered. 

Income  from  Residuals 

In  computing  the  credit  from  the  sale  of  residuals  in  each 
case,  it  is  assumed  that  the  total  coke  yield  is  60  per  cent  of  the 
central  district  coal  carbonized  and  65  per  cent  of  the  eastern 
coal,  and  that  15  per  cent  of  the  coke  in  the  former  case  and  8 
per  cent  of  the  coke  in  the  latter  case  is  breeze.  It  is  also  assumed 
that  the  screened  coke  brings  $9.00  per  ton,  and  the  breeze  $2.00 
per  ton  in  the  yard  in  each  case.  On  this  basis  the  income  per 
1,000  cubic  feet  of  gas  from  the  sale  of  coke  and  breeze  would 
amount  to  $0,546  and  $0,021  respectively  for  central  district  coal 
and  $0,512  and  $0,010  respectively  from  eastern  coal. 

It  is  assumed  that  the  central  district  coal  gives  an  ammonia 
recovery  of  5.5  pounds  per  ton  of  coal,  as  compared  with  5.0 
pounds  per  ton  from  eastern  coal,  and  that  a  net  price  of  $0.09 
per  pound  is  realized.  This  would  give  an  ammonia  credit  of 
$0,059  per  1,000  cubic  feet  of  gas  from  central  district  coal  and 
$0,043  per  1,000  cubic  feet  from  eastern  coal.  In  neither  case  is 
the  cost  of  handling  and  concentrating  considered,  it  being  as- 
sumed that  these  charges  will  be  proportional  to  the  yield  in  each 
case. 

The  tar  yield  is  assumed  to  be  10  gallons  per  ton  from  cen- 
tral district  coal  and  13.5  gallons  per  ton  from  eastern  coal.  A 
value  of  $0,035  per  gallon  for  the  tar  produced  gives  a  credit  of 
$0,042  and  $0,045  per  1,000  cubic  feet  of  gas,  respectively.  Here 
as  in  the  case  of  the  ammonia  the  handling  costs  are  neglected. 


ECONOMICAL  ADVANTAGES  23 

Summary  of  Costs 

Using  the  values  assumed  in  the  foregoing,  the  following 
comparison  for  the  two  kinds  of  coal  may  be  tabulated : 

Table  2. — A   comparison  of  the  approximate  manufacturing  costs  of  gas 

from  central  district   and  eastern   gas-coals. 

Central  district  coal       Eastern  coal 
Cost  per  M  cu.  ft.     Cost  per  M  cu.  ft. 
of  gas  of  gas 

Coal   carbonized   $0,476  $0,571 

Bench  fuel  .142  .120 

Purifying  expense  .014  .000 

CoaWiandling  labor  .024  .019 

Retort-house  labor  .178  .142 

Bench  and  retort  repairs  .056  .045 

$0,890  $0,906 

Income  from  residuals 

Coke    $0,546  $0,512 

Breeze  .021  .010 

Ammonia    .059  .043 

Tar    .042  .045 

$0,668  $0,610 

Cost  less  residuals  credit  .222  .296 

This  table  does  not  take  into  account  all  of  the  elements  of 
cost,  which  include  plant,  mains,  et  cetera,  but  only  those  which 
would  seem  to  be  affected  by  the  kind  of  coal  used,  it  being  as- 
sumed that  the  same  amount  of  gas  is  produced  in  each  case. 
Therefore  these  figures  are  not  presented  to  show  the  actual  cost 
of  gas  to  the  holder  but  merely  to  indicate  the  approximate  sav- 
ing in  manufacturing  cost  which  might  be  effected  by  the  use  of 
central  district  coals  under  the  conditions  assumed.  The  actual 
saving  will  vary,  and  some  operators  will  be  unable  to  substitute 
central  district  coal  completely  because  of  inadequate  equipment. 
Operators  are  urged  to  substitute  their  own  costs  in  the  fore- 
going tabulation  and  ascertain  whether  their  own  conditions  will 
not  permit  them  to  make  a  substantial  saving.  The  assumed  dif- 
ference in  cost  of  eastern  and  central  district  coals  is  the  chief 
item  underlying  the  calculations. 

SUMMARY 

A  majority  of  the  coal-gas  plants  in  Illinois  and  neighboring 
states  have  used  central  district  coals.  While  the  gas  yield  is 
smaller  and  the  coke  made  under  present  conditions  is  somewhat 


24  RETORT    COAL-GAS   MANUFACTURE 

inferior  to  that  from  eastern  coals,  many  plants  are  finding  the 
use  of  central  district  coals  profitable.  Since  the  use  of  these 
coals  would  do  much  to  release  railroad  cars  needed  for  war  pur- 
poses, it  is  a  patriotic  duty  to  use  them ;  furthermore,  their  use 
will  serve  to  protect  gas  companies  because  the  supply  will  be 
more  certain  during  periods  of  freight  congestion.  Experiences 
of  many  gas  companies  indicate  that  there  are  no  insurmount- 
able difficulties  preventing  the  use  of  these  coals  for  gas  making. 
A  more  exhaustive  study  of  the  conditions  affecting  the  use  of 
these  coals  is  needed  and  will  be  undertaken  in  the  near  future. 
All  gas  operators  who  are  not  now  using  central  district  coals 
should  carefully  consider  the  practicability  of  doing  so. 


PUBLICATIONS  OF 
ILLINOIS  MINING  INVESTIGATIONS 


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ILLINOIS  STATE  GEOLOGICAL  SURVEY  DIVISION 
URBANA,  ILLINOIS 

Preliminary  report  on  organization  and  method  of  investiga- 
tions, 1913. 

Chemical  study  of  Illinois  coals,  by  S.  W.  Parr,  1916. 

Coal  resources  of  District  I  (Longwall),  by  G.  H.  Cady,  1915. 

Coal  resources  of  District  VII,  by  Fred  H.  Kay,  1915. 

Coal  resources  of  District  VIII  (Danville),  by  Fred  H.  Kay  and 
K.  D.  White,  1915. 

Coal  resources  of  District  VI,  by  G.  H.  Cady,  1916. 

Coal  resources  of  District  II  (Jackson  Co.),  by  G.  H.  Cady, 
1917. 

Surface  subsidence  in  Illinois  resulting  from  coal  mining,  by 
Lewis  E.  Young,  1916. 

Tests  on  clay  materials  available  in  Illinois  coal  mines,  by 
R.  T.  Stull  and  R.  K.  Hursh,  1917. 

Carbonization  of  Illinois  coals  in  inclined  gas  retorts,  by  F.  K. 
Ovitz,  1918. 

The  manufacture  of  retort  coalrgas  in  the  central  states,  using 
low-sulphur  coal  from  Illinois,  Indiana,  and  western  Ken- 
tucky, by  W.  A.  Dunkley,  and  W.  W.  Odell,  1918. 


ENGINEERING  EXPERIMENT  STATION,  URBANA,  ILLINOIS 

Coal  mining  practice  in  District  VIII  (Danville),  by  S.  0. 
Andros,  1913. 

Coal  mining  practice  in  District  VII,  by  S.  O.  Andros,  1914. 

Coal  mining  practice  in  District  I  (Longwall),  by  S.  O.  An- 
dros, 1914. 

Coal  mining  practice  in  District  V,  by  S.  O.  Andros,  1914. 

Coal  mining  practice  in  District  II,  by  S.  0.  Andros,  1914. 

Coal  mining  practice  in  District  VI,  by  S.  0.  Andros,  1914. 

Coal  mining  practice  in  District  III,  by  S.  O.  Andros,  1915. 

Coal  mining  practice  in  District  IV,  by  S.  O.  Andros,  1915. 

Coal  mining  in  Illinois,  by  S.  0.  Andros,  1915.  (Complete  re- 
sume of  all  the  district  reports.) 

Subsidence  resulting  from  mining,  by  L.  E.  Young  and  H.  H. 
Stock,  1916. 

Percentage  of  extraction  of  bituminous  coal  with  special  ref- 
erence to  Illinois  conditions,  by  C.  M.  Young,  1917. 


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12. 
13. 

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U.  S.  BUREAU  OF  MINES,  WASHINGTON,  I).  C. 

Bulletin     72.     Occurrence  of  explosive  gases  in  coal  mines,  by  N.  H.  Darton, 

1915. 
The  humidity  of  mine  air,  by  R.  Y.  Williams,  1914. 
Mine  ventilation  stoppings,  by  R.  Y.  Williams,  1915. 
The  inflammability  of  Illinois  coal  dusts,  by  J.  K.  Clement 

and  L.  A.  Scholl,  Jr.,  1916. 
Use  of  permissible  explosives  in  the  coal  mines  of  Illinois,  by 

J.  R.  Fleming  and  J.  W.  Koster,  1917. 
Coking  of  Illinois  coals,  by  F.  K.  Ovitz,  1917. 
Technical  Paper  190.     Methane  accumulations  from  interrupted  ventilation, 

with  special  refrence  to  coal  mines  in  Illinois  and  Indiana, 

by  H.  I.  Smith  and  Robert  J.  Hamon,  1918. 


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